(-0.4x^2+50x)-(1.6x^2+12x+68)=0

Solution for (-0.4x^2+50x)-(1.6x^2+12x+68)=0 equation:

(-0.4x^2+50x)-(1.6x^2+12x+68)=0

We get rid of parentheses

-0.4x^2-1.6x^2+50x-12x-68=0

We add all the numbers together, and all the variables

-2x^2+38x-68=0

a = -2; b = 38; c = -68;
Δ = b2-4ac
Δ = 382-4·(-2)·(-68)
Δ = 900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{900}=30$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(38)-30}{2*-2}=\frac{-68}{-4}
=+17
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(38)+30}{2*-2}=\frac{-8}{-4}
=+2
$